Much attention has been given to the roles of aqueous humor production and transtrabecular outflow in the maintenance of the steady-state intraocular pressure. However, it has been found that uveoscleral outflow also may play a considerable part in the IOP lowering effects of certain glaucoma treatments. Since there had not been any non-invasive method to quantitate uveoscleral outflow, an investigation of uveoscleral outflow was impossible in humans. Recently, we have reported a fluorophotometric method to determine uveoscleral outflow and true trabecular outflow facility, which is non-invasive, and can be used repetitively in animals and humans - clearly a great advantage in glaucoma research. This method to determine true trabecular outflow facility avoids pseudofacility which is inherent in previous methods. To further establish the validity and reliability of our method, comparisons will be made in monkeys between the obtained values of uveoscleral outflow and trabecular outflow facility and those obtained using invasive procedures. A basic assumption of the fluorophotometric method, that acetazolamide and timolol do not affect uveoscleral outflow and episcleral venous pressure will also be tested. In humans, the fluorophotometric method will be used to study the roles of uveoscleral outfloW, true trabecular outflow facility, and aqueous humor production in the ocular hypotensive effects of topical epinephrine, topical prostaglandins, therapeutic ultrasound, and cyclodialysis. lt is hoped that these studies will lead to a better understanding of the basic mechanisms of action of these treatments and to more effective management of glaucoma.